/*
 *  Copyright 2012 GWT-Bootstrap
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package com.github.gwtbootstrap.client.ui.resources;

import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.HeadElement;

/**
 * Base class for classes that inject someting into the document header.
 * 
 * @since 2.0.4.0
 * @author Carlos Alexandro Becker
 * @author Dominik Mayer
 */
public abstract class AbstractInjector {

	private static HeadElement head;

	/**
	 * Gets the document header.
	 * 
	 * @return the document header
	 */
	protected static HeadElement getHead() {
		if (head == null) {
			Element element =
					Document.get().getElementsByTagName("head").getItem(0);
			assert element != null : "HTML Head element required";
			HeadElement head = HeadElement.as(element);
			AbstractInjector.head = head;
		}
		return AbstractInjector.head;
	}
}
